RH Mobile needs to run in Safari and be added to your Home screen to work the most effectively on your iPhone, iPad, or iPod.

Here's what you need to do:
Visit https://www.reporthost.com/mobile in Safari on your device.
To get RH Mobile installed you must first start it in a regular browser session.
This should be the only time you start RH Mobile in a browser. All other times will be from the Home screen icon.
Don't add your user!
Safari on iOS/iPadOS treats web apps as different entities when started from the browser and from the Home screen. Because of this, its better to never add your user at this point so that there's no confusion later.
Tap the share icon
Examples of the share icon are below and typically appear at the bottom of the screen (iPhone) or beside the address bar (iPad)
Choose 'Add to Home screen'
You'll probably have to scroll down (iPad and newer iPhone) or right (older iPhone) to find 'Add to Home screen' in the list of choices
After tapping 'Add to Home screen' there will be an 'Add' option in the top right corner.
Close the 'ReportHost Mobile' tab
Don't just close Safari or else RH Mobile will automatically be pulled up the next time you launch Safari. Instead, choose the tabs icon and X out of the RH Mobile tab.
Start RH Mobile from the Home screen
Wherever it was placed on your Home screen, or wherever you move it to, you'll launch RH Mobile with this icon.
Add your ReportHost user and enjoy!